The invention relates to a printing machine having a plurality of printing units for overprinting a plurality of inks on webs or sheets in one pass.
In modern printing plants, devices for producing printing forms, such as printing plates, and printing machines are provided in one machine room. Short transport paths between a device for producing printing forms or plates, and the various printing machines is intended to shorten the make-ready or set-up time of the printing machines. In printing plants with separate devices for producing printing forms or plates, it is necessary to mount the printing forms or plates belonging to a printing image in the printing units of a selected printing machine, and to position them in order to adjust the register. The printing forms or plates are brought into register during printing, this operation lasting a given length of time, and a number of misprints being produced during that time period.
In order to reduce the make-ready or set-up time further, printing machines are employed into which the device for producing the printing forms or plates is already integrated. Transport times from separate devices for producing printing forms or plates are thereby dispensed with, and the time for bringing the printing forms or plates into register is reduced, because the imaging has already been performed approximately in-register. Such a printing machine has been described heretofore in the published German Patent Application DE 197 43 770.2. The invention described in that document offers the possibility that, during printing with a printing machine, printing forms or plates for another print job are produced in the same printing machine. The object of the invention in the foregoing document is to increase the use of a previously existing raster image processor, and the connected imaging tools. The raster image processor data can be fed to selected imaging tools. Simultaneous printing and imaging is problematic, because the printing process can exert undesired influences upon the imaging.
It is accordingly an object of the invention of the instant application to provide a printing machine of the foregoing general type with improved efficiency and improved imaging quality.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a printing machine having a plurality of printing units for overprinting a plurality of inks in one pass, including a device for producing a printing form in each of the printing units, equipment for feeding to the device data for reproducing a printing image, and a tool responsive to the data for producing image points for accepting printing ink; a device for inking the printing forms and for transferring printing ink onto a printing material; and at least one computer for controlling imaging on the printing forms and for controlling the printing process, comprising a first memory for storing data for a first printing image that is produced from overprinting a plurality of printing inks, the plurality of printing inks being at least equal to the plurality of printing units; a second memory for storing data for a second printing image that is produced from printing with a plurality of printing inks that is at most equal to a difference between the plurality of printing units and the plurality of printing inks used for printing the first printing image; and a computer for effecting substantially simultaneous imaging on the printing forms for the first and the second printing images.
In accordance with another feature of the invention, the printing machine includes respective raster image processors for producing the printing forms for the first and the second printing images, respectively.
In accordance with a further feature of the invention, the printing machine includes a computer having a multitasking capability for producing the printing forms for the first and the second printing images.
In accordance with an added feature of the invention, the printing machine includes devices in each printing unit for removing the printing forms, those printing units having the printing forms of one of the images being operable together.
In accordance with a concomitant feature of the invention, the printing forms belonging to one printing image are removable from the printing machine while printing is being performed with the printing forms belonging to another printing image.
The invention permits simultaneous production of printing forms of two or even more printing images in one and the same printing machine. Printing forms belonging to one print job remain in a printing machine in order to process an existing print job. The printing forms belonging to a further print job or to a number of further print jobs are removed from the printing machine and are used for printing the further print jobs on the same printing machine or other printing machines.
The removal of the printing forms can be performed during printing. It is possible to produce a set of printing forms for a further print job in two or more partial steps. For example, in the case of a 6-color printing machine, in a first partial step, a set of printing forms for 4-color printing and a half set of printing forms for a 4-color print of a further printing machine are produced, and in a second partial step, a further set of printing plates for 4-color printing and the second half set of printing plates for the 4-color print on the further printing machine are completed. If the disposition of print jobs in a printing plant results in the situation wherein no current print job is to run on a printing machine according to the invention, then the printing machine can be used as an apparatus purely for producing printing forms. The outlay for implementing a printing machine according to the invention is low, because additional raster image processors or the multitasking capability of a computer necessitate only low additional costs. The control of the chronological sequence of the imaging of various printing images on printing forms can be performed in a manner that the imaging of all the printing forms is completed at virtually the same time. The input variable used for the chronological course or sequence of the imaging can be the number of image points to be set for the printing form or the area coverage values of the printing forms. By using such a printing machine, assurance is offered that the imaging device has virtually no idle time. The use of printing machines in a printing plant is improved.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a printing machine having a plurality of printing units for overprinting a plurality of inks in one pass, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, wherein: